I took my 556 to the range Saturday and after the first magazine the bolt failed to hold open. Before shooting it worked fine. I tried a Pmag, the factory Sig mag, and a Lancer L5 and had the same results with all of them. When I broke it open and inserted a magazine so I could see what was going on it appeared the magazine follower just wasn't pushing the bolt catch up all the way. If I pushed the lever on the outside of the rifle down the follower would spring up when the catch lifted. If I then depressed the release lever it on the outside the lever inside would depress the magazine follower and stick there. Any ideas what might be happening and how to correct it?